Check out ACME - I've seen some postings for EP III and IV cars recently

A quick search turns up these:
ACME #50275 (Jugoslaw JZ fast train coach, type Ba, second class, epoch III),
ACME #50278 (Jugoslaw JZ fast train coach, type Ca, third class, epoch III).

ACME #55090 looks interesting, but it is an epoch IV/V set of JZ and TCDD coaches for the Hellas Istanbul Express
ACME #55129 appears to be 3 more coaches to expand the 55090 set.

I'm sure there may be more if you have time to search.

Cheers!

Not quite era III, but almost: The TCDD international coaches similar to the Swiss BLS and SBB Schlieren types made by Sachsenmodelle some years ago, http://alte-modellbahnen...ierenwagen-der-TCDD.html

Do you have any specific (named and/or numbered) international trains in mind? Some more googling shows the following:

By 1962, the Orient Express and Arlberg Orient Express had stopped running, leaving only the Simplon Orient Express. This was replaced in 1962 by a slower service called the Direct Orient Express, which ran daily cars from Paris to Belgrade, and twice weekly services from Paris to Istanbul and Athens.

Looking up the Direct Orient Express:

There's a great picture here: http://www.trains-worldexpresses.com/200/208.htm and some more information.